1. Field of the Invention
The present invention relates to an information recording apparatus and method and an information processing apparatus using such an apparatus or method. More particularly, the present invention is concerned with an information recording apparatus and method for an optical disk medium such as a DVD-R (Digital Video or Versatile Disk-Recordable) or a DVD-RW (DVD-ReWritable), these disks having a format compatibility with reproduction-dedicated DVD media such as a video DVD and a DVD-ROM.
2. Description of the Related Art
With the spread of multimedia, there has been considerable activity in the development of reproduction-dedicated media such as a video DVD and a DVD-ROM, and information recording media such as a DVD-R and a DVD-RW. The DVD-R utilizes a dye or coloring matter to form a recording layer. The DVD-RW utilizes a phase-change substance in which a crystal phase and an amorphous phase are changed reversibly.
Information is recorded on a DVD as described above by a recording method as shown in FIGS. 1A through 1D, in which the horizontal axes present the radial position on the DVD. FIG. 1A schematically shows a format of the DVD. As shown in FIG. 1D, data (sectors) are successively recorded on all tracks at a constant liner density.
In order to provide information recording media that have a format compatibility with the reproduction-dedicated media, the rotational velocity of the media is controlled by a CLV (Constant Linear Velocity) method in which the number of revolutions of the DVD is inversely proportional to the track radius, as shown in FIG. 1B. Thus, as shown in FIG. 1C, information is recorded on the DVD at a constant channel clock frequency for recording while the linear velocity of the tracks is kept constant irrespective of the track position.
In order to control the rotational velocity by the CLV control, it is required to change the number of revolutions of the DVD in order to maintain the linear velocity of the tracks at a constant. More particularly, it is required to change the number of revolutions of a spindle motor which drives the DVD. Thus, the spindle motor requires a large revolution torque. Such a spindle motor is of a large size and is expensive. Additionally, it takes a long time to complete a change of the velocity of the spindle motor in seek operation. This leads to an extremely long access time, as compared to an HDD and an MO drive.
Under the above-mentioned circumstance, it is desired to record information on the media while keeping the number of revolutions thereof at a constant. With the above in mind, a recording method shown in FIGS. 2A through 2D has been proposed. As shown in FIG. 2C, the frequency of the channel clock for recording is changed in such a way as to be proportional to the track position in the radial direction. More particularly, the frequency proportionally increases as the track position moves from the inner circumference to the outer circumference. In this case, the recording linear velocity is comparatively low in the inner portion and is comparatively high in the outer portion. Thus, as shown in FIG. 2D, the recording linear density can be kept constant. Information can be recorded on the DVD by a CAV (Constant Angular Velocity) control in which the number of revolutions (rotational velocity) of the DVD is fixed, as shown in FIG. 2B.
Consequently, there is no need to perform the revolution changing control of the spindle motor, so that a compact, less-expensive spindle motor with a small revolution torque can be employed. Further, there is no need for the time necessary for completing a change of the revolution speed, so that the access time can be drastically reduced.
However, a specific attention should be drawn to the dye-based DVD-R media and DVD-RW media of phase-change type in which a pit (mark) is formed thereon in a heat mode. In these media, the pulse widths of a train of recording pulses of a laser beam at the time of recording and a recording power are respectively optimized at a particular recording linear velocity. Thus, for a different recording linear velocity, the mark formed by the pulse train and a space sandwiched by adjacent marks have different states. For example, a top heating pulse necessary for forming a mark may not have a sufficient thermal capacity, and the temperature obtained by heating thereof is different from the optimal decomposition temperature. As a result of the above, the average length of the marks may be dispersed and the pulse width of the tail pulse of the pulse train may deviate from the optimal pulse width so that the even mark width cannot be obtained. There is also a possibility that the mark may have a relatively wide or narrow width (a tear-like mark may be formed) depending on the mark length. The above-mentioned facts degrade the jitter characteristic.
With regard to the above-mentioned problems, Japanese Laid-Open Patent Application No. 5-225570 proposes an improved method for obtaining the optimal amount of light for recording. The proposed method is particularly intended to obtain the optimal amount of light for recording that can be applied to all recordable areas of individual disks with a reduced time. More particularly, the optimal amounts of light for recording are obtained in at least two positions in a trial writing area on the optical disk by using recording linear velocities equal to those at positions in the user recording section. The trial writing area is located in one or both of the innermost and outermost circumference positions. Then, an interpolation routine is performed in which the two optimal amounts of light for the two recording linear velocities are subjected to an interpolation or extrapolation process. Thus, the optimal amounts of light for recording at all recording linear velocities can be obtained.
There is another proposal disclosed in Japanese Laid-Open Patent Application No. 5-274678. The proposal is directed to reducing laser power necessary for recording without degrading the jitter characteristic. More particularly, the proposal projects, onto the optical disk, an optical beam that is intensity-modulated in accordance with information in synchronism with different reference clocks that depend on areas for recording while the optical disk is rotated at a constant velocity. Thus, information can be recorded on an outer-circumference area at a frequency higher than that at which information is recorded on an inner-circumference area. The optical beam is periodically emitted in a pulse formation at a frequency equal to an integer multiple of the frequency of the reference clock involved in the area on which information should be recorded. In addition, the duty ratio involved in pulse emission is larger in the outer-circumference portion than that in the inner-circumference portion.
Yet anther proposed method is described in Japanese Laid-Open Patent Application No. 10-106008. The application discloses an optical disk drive capable of recording information at an increased rate with high reliability, the drive being equipped with an optical disk, an optical head, synchronizing signal generating means, a VCO (Voltage-Controlled Oscillator), phase comparing means, a controller and recording signal generating means. The pulse height and width of the recording signal are changed dependent on the recording linear velocity so that information can constantly be recorded in the optimized condition.
The proposals described in the above-identified applications control to change a factor involved in the recording pulses such as the duty ratio of pulse emission dependent on the recording linear velocity in the CAV control. However, the proposals yield only qualitative effects on the optical disk media, but do not yield sufficient effects on the DVD media. More specifically, variations in the characteristics of recording information (an RF signal), such as the jitter characteristic, depend on an interaction on a plurality of factors. In practice, the proposed method is not capable of recording information on the DVD media with uniform signal characteristics over the entire surface of the optical disk. Thus, the desired results may not be obtained. No quantitative consideration regarding the ways to change the values of the parameters of the recording pulses is given.
In a case where the parameter values with regard to the recording pulses consisting of the top heating pulse and subsequent heating pulses are changed, the modulation factor or asymmetry may be changed before and after the setting of the parameter values is changed. Thus, a thrice or threshold level for binarization cannot timely follow a change in the modulation factor or asymmetry, so that the jitter characteristic may be degraded.
It is a general object of the present invention to eliminate the above-mentioned disadvantages.
A more specific object of the present invention is to record information on the entire recording surface of an optical disk with an even signal characteristic by means of a simple control without changing the rotational velocity of the optical disk while maintaining a compatibility with a recording format of conventional reproduction-dedicated media.
Another object of the present invention is to suppress variations in the thrice level for binarization and prevent degradation of the jitter characteristic.
Yet another object of the present invention is to correct an edge shift of a mark due to heat accumulated in the optical disk with respect to all possible recording linear velocities in recording based on CAV control and thus accomplish jitter-reduced recording on the entire recording surface.
The above objects of the present invention are achieved by an information recording method for recording information on an optical disk by a recording pulse train of an optical beam emitted by an optical source, said method comprising the steps of: (a) changing a recording channel clock period T in accordance with a change of a recording linear velocity so that a recording linear density is kept constant; and (b) updating values of parameters Ttop, Tmp and xcfx81 at intervals based on a desired recording linear velocity, where Ttop is a ratio of a width of a top heating pulse in the recording pulse train to the recording channel clock period T, Tmp is a duty ratio of each heating pulse in a multi-pulse section following the top heating pulse, and xcfx81 is a ratio of a recording power Pw at the desired linear velocity to an optimal recording power Pwmin at a minimum recording linear velocity (xcfx81=Pw/Pwmin).
The above objects of the present invention are also achieved by an information recording method for recording information on an optical disk by a recording pulse train of an optical beam emitted by an optical source, said method comprising the steps of: (a) changing a recording channel clock period T in accordance with a change of a recording linear velocity so that a recording linear density is kept constant; and (b) updating a setting value of a pulse width of a top cooling pulse in the recording pulse train at intervals based on a desired recording linear velocity by changing a front edge position of the top cooling pulse so that the pulse width of the top cooling pulse is different from pulse widths of cooling pulses in a multi-pulse section of the recording pulse train following the top cooling pulse.
The above-mentioned objects of the present invention are also achieved by an information recording method for recording information on an optical disk by a recording pulse train of an optical beam emitted by an optical source, said method comprising the steps of: (a) changing a recording channel clock period T in accordance with a change of a recording linear velocity so that a recording linear density is kept constant; and (b) updating setting values of pulse widths and recording power of heating pulses included in the recording pulse train at intervals so that a front edge position of a top heating pulse included in the recording pulse train, a rear edge position of a tail heating pulse included therein, and a recording power of the heating pulses included therein are changed in accordance with a desired recording linear velocity.
The above-mentioned objects of the present invention are also achieved by an information recording method for recording information on an optical disk by a recording pulse train of an optical beam that is emitted by an optical source, said method the steps of: (a) changing a recording channel clock period T in accordance with a change of a recording linear velocity so that a recording linear density is kept constant; and (b) updating setting values of a waveform of a first heating portion of the recording pulse train followed by a second heating portion at intervals in accordance with a desired recording linear velocity so that a width of the first heating portion and a recording power thereof are changed.
The above-mentioned objects of the present invention are also achieved by an information recording method for recording information on an optical disk having a recording layer in which a crystal phase and an amorphous phase are changed reversibly by a recording pulse train of an optical beam emitted by an optical source, said method comprising the steps of: (a) changing a recording channel clock period T in accordance with a change of a recording linear velocity so that a recording linear density is kept constant; and (b) updating values of at least two of parameters Ttop, Tecp and E at intervals based on a desired recording linear velocity, where Ttop is a ratio of a width of a top heating pulse in the recording pulse train to the recording channel clock period T, Tecp is a ratio of a width of an end cooling pulse in the recording pulse train, and E is a ratio of a erasing power Pe to a heating power Pw.